Sterilizable centrifugal atomizer for spray driers



A. MQLLER Nov. 10, 1959 STERILIZABLE CENTRIFUGAL ATOMIZER FOR SPRAYDRIERS Filed Nov. 14, 1957 2 Sheets-Sheet l M. v I'll AAGE MQLLERINYENTOR :XuflPnM/ AH' s STERILIZABLE CENTRIFUGAL ATOMIZER FOR SPRAYDRIERS Filed Nov. 14, 1957 A. MQLLER Nov. 10, 1959 2 Sheets-Sheet 2INYENTOR E R AAGE Mou.

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ATTORNEYS L ,chamber of known type.

STERILIZABLE CENTRIFUGAL ATOMIZE FOR SPRAY DRIERS The invention relatesto a sterilizable centrifugal atomizer. Such atomizers are e.g. used forthe production of powders by the atomization of a liquid in a dryingchamber. The invention also relates to a device comprising such atomizerfastened in the walls of a closed vessel in which the atomization anddrying of the liquid take place.

The invention has for its object to provide an improved centrifugalatomizer which can be sterilized effectively before being put intooperation and which can be maintained sterile during the operation:

In a device for the production of powders which'have to be sterile, e.g.medical preparations, the atomizer is generally sterilized, before beingstarted, by means of sterilizing vapour. During the operation sterilizedcompressed air is supplied to the atomizer in order to prevent bacteriafrom entering the sterilized parts thereof. The vapour should beprevented from entering the shaft journals and the gear box of theatomizer, because there it would cause damage, and therefore it isnecessary to make a sealing between the place where the vapour issupplied to the atomizer and said journals and gearbox. An ordinarypacking cannot be used for this purpose because of the very rapidrotation of the atomizer shaft, and further such packing would preventthe flow of the sterilized compressed air through the journals whichwould be a disadvantage since this very flow prevents bacteria fromentering the sterilized part of the atomizer and further preventsforeign materials, as e.g. oil drops from the journals, from reachingthe sterilized atomization wheel. 7 V According to the invention theatomizer comprises valve means which can provide the necessary sealingand which can be opened and closed by the axialdisplace- .ment of theatomizer shaft.

Another object of the invention is means for axial displacement of saidshaft between two positions, in one of which the valve means is closedand in the other of which, corresponding to the operational condition ofthe atomizer, the valve means is open.

A further object of the invention is means for preventing the startingof the atomizer when the shaft is'not :in its operational position.

Other and further objects and advantages of the invention will appearfrom the following description referring to the accompanying drawingsshowing an embodiment of the invention, V

Fig. 1 illustrates partly in section, an apparatus comprising anatomizer according to the invention,

Fig. 2 illustrates on a larger scale and partly in'section the atomizershown in Figi Fig. 3 is a view in the direction of arrows III in Fig. 4,and

Figs. 4 and 5 are sectional views, corresponding to ,:Fig. 2 but on alarger scale, of the upper and lower parts, :respectively, of theatomizer shaft.

Fig. 1 shows a closed vessel 101 enclosing a drying v In the upper part1 of said vessel is an atomizer according to the invention, of whichStates Paten a screen 2, a top part 4, and an electric motor housing 13may be seen in Fig. 1. Further, the atomizer wheel 21 proper is shown. Atube 34 serves for supplying the liquid to be atomized and another tube102 serves for supplying a drying medium, as e.g. hot air, to thechamber. Finally, a tube 41 is shown, the purpose of which is to supplysterilizing vapour and sterilised compressed air, and which may, througha changeover valve 103, be selectively connected to tubes 1614 andleading to devices for supplying vapour and compressed air,respectively.

As will appear from Fig. 2, the atomizer housing comprises besides thescreen 2 and the top part 4, also a bottom part 5 secured to said toppart 4 by means of screws 6. The top part is screwed onto the screen 2by screws 7 and rests on the upper part or roof 1 of the drying chamber.The bottom part5 fits into a ringshaped member 3, and a seal betweenthese two parts is provided by means of a sealing ring 8.

The top part 4 contains a gear box 9 closed by a lid 10 secured by .aring 11 screwed onto the top part by means of screws 12. The lid 10 isintegral with the housing 13 of the electric motor, the shaft 14 ofwhich penetrates into the gear box 9 and carries a gear wheel 15 in meshwith a gear wheel 16.

At one side of the gear box 9 there is an inspectionglass 17, which issecured by means of a nut 19 and sealing rings 18 to top part 4, andthrough which the rotation of the gear wheels may be observed and theoil level of oil in the gear box checked.

To one end of a shaft 20, projecting from one end of the housing, theatomizer wheel 21 is secured by means of a washer 22 and the nuts 23 and24 (see also Fig. 5) whereas the other end of the shaft 20 carriesv thegear wheell (see also Fig. 4). In the atomizer wheel 21 there isprovided a circular groove 25 concentric with the shaft 20. The limitingwall of the groove 25 nearest the shaft 20 has steps 26. From the groove25 a number of channels having rectangular cross-section and the inletsof which are designated 27, extend to the periphery of the atomizerwheel. The open channels are covered by a lid 28 secured to the atomizerwheel 21 by means of rivets 29 so as to form closed channels ofrectangular cross-section.

Immediately above the atomizer wheel but without contacting said wheel,a so-called liquid distributorfis disposed, said distributor beingconstituted by a circular disc 30 which by means of a vertical flange 31is screwed onto the bottom part 5. In the disc 30 there is a groove 32concentric with the shaft 20 which com,- municates with a number ofholes 33. The supply tube 34 for the liquid to be atomized opens intothe groove 32 and at the other end has a pressure-tight connection at aflange on the top part comprising a stufiing box 35 and a packing gland36. The tube 34 ends at top in a threaded connection 37.

During operation, the shaft 20 and consequently also the atomizer wheel21 is set into rapid rotation by means of the electric motor whichdrives the shaft through the gear wheels 15 and 16. The shaft 20 isjournalled in ball bearings 38 and 39, the construction of which will beexplained in detail below. The liquid to be atomized is supplied to theupper end of the tube 34, flows through said tube into the groove 32,from where it continues through the holes 33 down on the steps 26 in theatom-' izer wheel 21 where, as a consequence of the centrifugal force,it will be flung outwards in a radial direction towards the outer wallof the groove 25 where it flows in through the inlets 27 into thechannels of rectangular cross-section. Likewise as a consequence of thecentrifugal force, the liquid flows further outwardly through thechannels until with great velocity it gets to the circumference of theatomizer wheel, from which the atomization of the liquid takes place.The steps 26 have for their purpose to cause an even distribution of theliquid over the cross-section of the inlets 27 of the channels, and acircular flange 40 on the disc 30 has for its purpose to prevent liquidfrom being flung out of the atomizer through the space between the lid28 of the atomizer wheel and the disc 30.

As the atomizer is designed for use in a device for the production ofsterile substances, the parts of the atomizer and also the other partsof the device coming into contact with the liquid to be atomized and thepowder produced, must be sterilized before the atomizer is put intooperation. Therefore, the atomizer comprises the supply tube 41 forsterilizing vapour, said tube extending by means of an air tightconnection through the flange of the upper part 4 through a stufiing box42 and a packing gland 43. The tube 41 which at the top is provided witha threaded connection 44 at its lower end 46 opens into a firstcompartment 45 defined by partitions in the housing and surrounding theshaft 20 adjacent to the projecting end thereof.

The vapour supplied through the tube 41 will flow downwards from thecompartment 45, along the shaft 20 and then outwards through the spacebetween the disc 30 and the atomizer wheel 21 filling and sterilisingeffectively all cut-outs and cavities in the disc 30 and the atomizerwheel 21.

However, from the compartment 45 the vapour will also tend to flowupwards along the shaft 20 and will, if no other measures are taken,penetrate into a second compartment constituted by spaces 47 and 48,which are also defined by partitions in the housing and in which thebearing 39 for the shaft are located, and possibly further upwardsthrough the bearing 38 and the gear box 9. As the vapour has adetrimental effect on the ball bearings and the gear wheels, the latterflow of vapour must be prevented. The use of a conventional packing forthis purpose situated in the passage between the compartments 45 and 47has proved to be ineffective in an atomizer of the type herein describedon account of the very high speed of rotation of the shaft 20.Consequently, provision has been made in said passage of a valve meansso constructed that when the shaft 20 is axially displaced from itsposition of operation, viz. the position shown in Fig. 2, the valvemeans provides a vapor-tight seal between the compartment 45 on one handand the compartments 47, 48 and 9 on the other hand. This valve meanscomprises a first member consisting of a steel ring 49 which is shrunkonto and forms a vapour-tight seal with the shaft 20 and a second memberconsisting of a plastic bushing 50 which is pressed into and forms avapour-tight seal with a cylindrical part 51 of the bottom part 5, whichcylindrical part surrounds the shaft 20, said bushing being providedwith a hole in which the shaft 20 can freely move. The ring 49 has acontact surface 52 at right angles to and surrounding the shaft 20, andthe bushing 50 has a corresponding contact surface 53. The distancebetween the two surfaces 52 and 53 is so chosen that by the axialdisplacement of the shaft 20 from its position of operation, they can bebrought into engagement with one another whereby a vapourtight sealbetween the spaces 45 and 47 is provided. For the purpose of furthersecuring a vapour-tight seal, the surface 53 is provided with a numberof ribs 54 concentric with the shaft 20.

For the purpose of obtaining the axial displacement, the shaft 20 isjournalled in the following manner. The ball bearing 39 is secured tothe shaft 20 between the ring 49 and a shoulder 55 and is displaceablein an axial direction in a ring 56 which is prevented from being axiallydisplaced by a shoulder 57 on the bottom part and a locking ring 58 inthe top part 4 and from being turned by a pin 59. To prevent thelubricant used for lubricating the ball bearing 39 from pcntraiing downinto the compartment 45, the ring 49 and the bushing 50 are designed asa conventional labyrinth seal which causes the lubricant to be collectedat the bottom of the compartment 47 from which it is pumped up by meansof a hand pump 69, the suction opening 61 of which is shown in Fig; 2.The ball bearing 38 (see also Fig. 4) is secured on the shaft 20 betweena steel bushing 62 which is shrunk onto the shaft 20, and a cylindricalbushing 63 which is secured against axial displacement by a clampingdevice consisting of parts 64 and 65. The ball bearing 38 isdisplaceable in an axial direction in a cylindrical bushing 66 securedto the top part 4 by means of screws 67 and in the operative position ofthe atomizer is pressed against an inwardly projecting flange 68 on thebushing 66 by a number of disc springs 69 which rest against a lockingring 70. The bushing 62 and the flange 68 are designed as a labyrinthseal to prevent the lubricant for the gear wheels 15 and 16 frompenetrating into the ball bearing 38.

When the shaft is not influenced by external axial forces, under theeffect of the springs 69 operating through the ball bearing 38, it willbe kept at an upper position, i.e. at the operative position, in whichthe surface 52 and the surface 53 with the ribs 54 do not contact eachother, and in which the shaft 20 can, therefore, rotate freely in thebearings 38 and 39.

The axial displacement of the shaft 20 required for closing the valvemeans in the embodiment shown is provided by an adjusting meanscomprising a rod 71 which is shown in detail in Fig. 3, and which has acylindrical portion 72 of small diameter, and an adjacent conicalportion 73. By means of a cylindrical portion 74, the rod 71 is mountedin the wall 4 of the gear box in a bushing 75. A thread 76 is inengagement with a threaded bushing 77 in the wall 4 of the gear box. Oneend of the rod 71 is provided with a hand-wheel 78.

In the operative position of the atomizer, the rod is screwed as far tothe right, Fig. 3, as possible. In this position, the cylindricalportion 72 is located above the uppermost end of the shaft 20 which,however, it does not touch, see Figs. 2, 3 and 4, in that the upwardsmovement of the shaft 20 is limited by the abutment of the ball bearing38 against the flange 68. If the rod is rotated so as to move to theleft, Fig. 3, the cylindrical portion 74 is displaced in the bushing 75,and the conical portion 73 moves over the end of the shaft 20 which isthereby displaced downwards against the force of the springs 69 untilthe ribs 54 abut the surface 52 thereby securing a vapour-tight sealingbetween the compartments 47, 48 and 45.

Since the valve means would be damaged if the atomizer was started withthe valve means in the closed position, provision has been made formeans for preventing such starting, said means comprising a pin 79resting against the stationary portion of the ball bearing 38 andextending through holes in the flange 68 and the lid 10 to the topsurface of said lid, where the pin 79 operates an electric switch 80which is closed only when the ball bearing 38 and consequently the shaft20 are in their top positions, and the two parts 49 and 50 of the valvemeans are, therefore, not in engagement with one another. The

switch 80 is connected in the electric circuit of the motor and preventsthe motor from being started when the shaft 20 is not in its operativeposition.

When starting the device, the following operations should be made.

At first, the rod 71 is turned so as to move to the left, Fig. 3,whereby the valve means is closed in the manner stated above. Next, thechange-over valve 103 is so positioned that vapour is supplied from thetube 104 through the tube 41 from which it flows through the tube end 46into the compartment 45 and from there downwards along the shaft 20 andout through the space between the atomizer wheel 21 and the disc 30 ofthe liquid distributor. 0n the other hand the vapour canr S V not flowupwards into compartments 47, 48 and 9 and cannot, therefore, damageball bearings and gear wheels. When the atomizer has been sterilised theposition of change-over valve 103 is changed so that sterilisedcompressed air is now supplied from the tube 105 instead of vapour.Then, the shaft 71 is turned so as to move to the right, Fig. 3, wherebythe shaft 20 is brought into its operative position. The atomizer cannow be started and the liquid to be atomized supplied through the tube34.

Besides flowing downwards along the shaft 20, the sterilised compressedair supplied as long as the atomizer is in operation flows also upwardsalong said shaft, through the valve means and the ball bearings into thegear box where it escapes through casual leaks. This flow of sterilisedcompressed air has for its purpose to prevent bacteria from making theirway from the nonsterilised part of the atomizer into the sterilisedpart, and further to prevent impurities, for example, oil drops from theball bearing 39, from penetrating to the atomizer wheel. For the purposeof increasing the resistance of flow of the downwardly-directed flow ofcompressed air and, consequently, insuring that a suitable part of thesupplied compressed air flows upwards, the disc 30 of the liquiddistributor is provided with a number of circular grooves 81.

The invention is not limited to the embodiment shown on the drawing.Thus, the two members 49 and 50 of the valve means need not to be madeof the above materials. They can both be of the same material, forexample plastic or steel, in which latter case some kind of packing isexpediently placed between the members. The two members 49 and 50 neednot be separate parts secured to the shaft 20 and the bottom part 5,respectively, but may be integral with and, consequently, of the samematerial as 20 and 5, respectively. If the members 49 and 50 are made ofmaterials which in themselves provide a sealing effect when the surfaces52 and 53 are pressed together, the ribs 54 may be omitted.

The supply tube 41 for vapour and compressed air may consist of twoseparate tubes, whereby the change-over valve 103 may be omitted.

For the axial displacement of the shaft 20, other means than those shownon the drawing can be used. The main thing is that the shaft 20 has adefinite position of operation where it is prevented from being axiallydisplaced, and that when not in operation it can be displaced enough sothat the valve means closes the passage between the first compartmentand the other compartment(s). If a spring load is used, the direction ofthe spring force may be opposite the direction used in the embodiment,in which case the sealing is effected by means of the spring pressurewhile the shaft must be kept in the operative position by means of aspecial device acting through one or both of the bearings.

The adjusting means need not be a rod having a conical portion andextending at right angles to the atomizer shaft. For example, it can beconstituted by a rod or pin being parallel with, and adjustable in, thedirection of the shaft, said rod or pin acting either directly on theshaft or through one of the bearings of said shaft.

What I claim is:

l. Sterilizable centrifugal atomizer comprising a housing, bearingsmounted in said housing, a shaft rotatably journalled in said bearings,one end of said shaft projecting from one end of said housing, anatomizationwheel fastened to said projecting end of said shaft, meansfor rapid rotation of said shaft, means for the supply of the materialto be atomized to said wheel, a first partition in said housing definingwith said housing a first compartment surrounding said shaft adjacent tosaid projecting end thereof, a second partition in said housing spacedfrom said first partition and defining therewith and with said housing asecond compartment also surrounding Said shaft, one of said bearingsbeing in said second 6 partition, said first partition being spaced fromsaid shaft to leave a passage therethrough interconnecting said firstand said second compartments and surrounding said shaft, means bearingon said shaft for axial'displacement of said shaft, valve means situatedin said passage and operable by said shaft when it is axially displaced,and supply means connected to said first compartment for separate supplyof sterilizing vapour and of sterilized compressed air to said firstcompartment.

' 2. Sterilizable centrifugal atomizer as claimed in claim 1, whereinsaid means for the supply of sterilizing vapour and sterilizedcompressed air comprises a single tube opening at one end into saidfirst compartment and having at the other end selection means forseparate supply of sterilizing vapour and sterilized compressed air.

3. Sterilizable centrifugal atomizer comprising a housing, bearingsmounted in said housing, a shaft rotatably journalled in said bearings,one end of said shaft projecting from one end of said housing, anatomization wheel fastened to said projecting end of said shaft, meansfor rapid rotation of said shaft, means for the supply of the materialto be atomized to said wheel, a first partition in said housing definingwith said housing a first compartment surrounding said shaft adjacent tosaid projecting end thereof, a second partition in said housing spacedfrom said first partition and defining therewith and with said housing asecond compartment also surrounding said shaft, one of said bearingsbeing in said second partition, said first partition being spaced fromsaid shaft to leave a passage therethrough interconnecting said firstand said second compartments and surrounding said shaft, valve meanssituated in said passage and comprising a first member tightlysurrounding and secured to said shaft and a second member securedtightly to said housing and having an aperture therein, said shaftextending freely through said aperture, each of said first and saidsecond members having a contact surface surrounding said shaft, saidsurfaces on said first and said second members facing each other, meansacting on said shaft for the maintenance of said shaft in a firstposition with said contact surfaces pressed against each other,resilient means bearing on said shaft for axial displacement of saidshaft from said first position to a second position with a space betweensaid surfaces and for the maintenance of said shaft in said secondposition, and supply means connected to said first compartment forseparate supply of sterilizing vapour and of sterilized compressed airto said firstcompartment.

4. Sterilizable centrifugal atomizer as claimed in claim 3, wherein saidcontact surfaces on said first and said second members are substantiallyplane and at right angles to said shaft.

5. Sterilizable centrifugal atomizer as claimed in claim 3, wherein thatportion of one of said first and second members having said surfaceconsists of a resilient material.

6. Sterilizable centrifugal atomizer as claimed in claim 3, wherein anumber of endless ribs are present on one of said surfaces, said ribsbeing concentric with said shaft.

7. Sterilizable centrifugal atomizer comprising a housing, bearingsmounted in said housing, a shaft rotatably journalled in said bearings,one end of said shaft projecting from one end ofsaid housing, anatomization wheel fastened to said projecting end of said shaft, meansfor rapid rotation of said shaft, means for the supply of the materialto be atomized to said wheel, a first partition in said housing definingwith said housing a first compartment surrounding said shaft adjacent tosaid projecting end thereof, a second partition in said housing spacedfrom said first partition and defining therewith and with said housing asecond compartment also surrounding said shaft, one of said bearingsbeing in said second partition, said first partition being spaced fromsaid shaft to leave a passage therethrough interconnecting said firstand said second compartments and surrounding said shaft, adjusting meansbearing on said shaft for axial displace ment of saidshaft, saidadjusting means being situated adjacent to the other end of said shaftand being adjustable in the axial direction of said shaft, spring meansacting on said shaft for the maintenance of said shaft in engagementwith said adjusting means, valve means situated in said passage andoperable by said shaft when it is axially displaced, and supply meansconnected to said first compartment for separate supply of sterilizingvapour and of sterilized compressed air to said first compartment.

8. Sterilizable centrifugal atomizer as claimed in claim 7, wherein saidadjusting means comprises an adjusting rod at right angles to said shaftand having a conical part thereon situated adjacent to said other end ofsaid shaft, and means for axial displacement of said adjusting rod.

9. Sterilizable centrifugal atomizer comprising a housing, bearingsmounted in said housing, a shaft rotatably journalled in said bearings,one end of said shaft projecting from one end of said housing, anatomization wheel fastened to said projecting end of said shaft, anelectric motor for rapid rotation of said shaft, means for the supply ofthe material to be atomized to said wheel, a first partition in saidhousing defining with said housing a first compartment surrounding saidshaft adjacent to said projecting end thereof, a second partition insaid housing spaced from said first partition and defining therewith andwith said housing a second compartment also surrounding said shaft, oneof said bearings being in said second partition, said first partitionbeing spaced from said shaft to leave a passage therethroughinterconnecting said first and said second compartments and surroundingsaid shaft, means bearing on said shaft for axial displacement of saidshaft between a first and a second position, valve means situated insaid passage and operable by said shaft when it is axially displaced toa closed condition in said first position of said shaft and to an opencondition in said second position of said shaft, an electric switchconnected in the electric circuit of said electric motor, mechanicalmeans contacting said switch for the movement of said switch to theon-position only when said shaft is in said second position, saidmechanical means contacting and being moved by said shaft, and supplymeans connected to said of said shaft, means for the supply of thematerial to be atomized to said wheel, a first partition in said housingdefining with said housing a first compartment surrounding said shaftadjacent to said projecting end thereof, a second partition in saidhousing spaced from said first partition and defining therewith and withsaid housing a second compartment also surrounding said shaft and, oneof said bearings being in said second partition, said first partitionbeing spaced from said shaft to leave a passage therethroughinterconnecting said first and said second compartments and surroundingsaid shaft, means bearing on said shaft for axial displacement of saidshaft, valve means situated in said passage and operable by said shaftwhen it is axially displaced, and supply means connected to said firstcompartment for separate supply of sterilizing vapour and of sterilizedcompressed air to said first compartment. I

11. Device as claimed in claim 9, wherein said means for the supply ofsterilizing vapour and sterilized compressed air comprises a single tubeopening at one end into said first compartment, a change-over valve onthe other end of said tube, a second tube connecting said change-overvalve to a device for the supply of sterilizing vapour, and a third tubeconnecting said change-over valve to a device for the supply ofsterilized compressed air.

References Cited in the file of this patent UNITED STATES PATENTS2,584,973 Andermatt Feb. 12, 1952 FOREIGN PATENTS 481,786 Canada Mar.18, 1952 760,660 Great Britain Nov. 7, 1956

